In recent years, photoacoustic tomography (PAT) imaging apparatuses (PAT apparatuses) have been developed in the medical field. PAT apparatuses excite absorbing materials inside an object by irradiating the object with optical pulses, and detect photoacoustic signals generated by thermoelastic expansion of the absorbing materials, so as to form images of properties of the object related to optical absorption. That is to say, images of an optical energy deposition amount distribution (optical energy absorption density distribution) inside the object with respect to irradiation light are formed. Also, based on this, images of an optical absorption coefficient distribution in the object related to an irradiation wavelength are formed. Furthermore, based on optical absorption coefficient distributions related to a plurality of wavelengths, images of the states of materials constructing the object (e.g., oxygen saturation of hemoglobin) can also be formed. These images are expected to make visible information related to new blood vessels generated inside and outside a tumor, such as cancer. Hereinafter, these images are collectively referred to as photoacoustic tomography images (PAT images).
With PAT apparatuses, irradiation is performed with near infrared ray pulses with a small energy, and therefore it is difficult to form images of deep parts of an object compared to the case of X-rays and like. In view of this, in Japanese Patent Laid-Open No. 2010-88627, imaging is performed in a state where a breast is held by two flat plates (hereinafter referred to as holding plates) and reduced in thickness in one form of a PAT apparatus using the breast as an object.
Japanese Patent Laid-Open No. 2007-29353 discloses a technique to display an X-ray irradiation field and an X-ray detection field as visually distinguishable pictures in such a manner that they are overlapped over an appearance image obtained by imaging a body surface of an object with a camera.
However, the technique of Japanese Patent Laid-Open No. 2010-88627 or Japanese Patent Laid-Open No. 2007-29353 is problematic in that, in a case where a region of attention in the object is not on the body surface but is inside the body of the object, an accurate range of the region of attention is unknown even with the use of marks on the body surface as reference information, and therefore it is difficult to appropriately set an imaging region.
In view of the above problem, the present invention provides a technique to set an imaging region such that a region of attention inside an object is imaged appropriately.